1. Field of the Invention
The present invention relates to a laser machining apparatus for machining with a laser beam a workpiece placed on a movable stage.
2. Related Background Art
A conventional machining apparatus of this type is used as a semiconductor manufacturing apparatus. In particular, in a conventional machining apparatus for wafer repairing wherein a processed wafer is reprocessed with a laser beam, a wafer must be aligned with a laser beam radiation position with high precision at high speed.
Typical conventional methods of aligning a workpiece to a laser beam radiation position in a conventional machining apparatus are a method of shifting a stage which supports the workpiece and a method of shifting a laser beam radiation position by using an optical system such as a galvano mirror.
The method of shifting the stage has an advantage in that the stage can be aligned to the laser beam radiation position with high precision. However, due to a large mass of a workpiece carrying stage and its drive mechanism, high-speed alignment cannot be performed in this method.
The method of shifting the laser beam advantageously allows high-speed shifting of the laser beam. However, alignment precision for aligning the laser beam spot on a predetermined target position on the workpiece cannot be improved much.